1. Field of the Invention
The present invention relates generally to a microelectromechanical system (MEMS), and more particularly to a MEMS and process of making the same for lowering interference.
2. Description of the Prior Art
A microelectromechanical system (MEMS) is a combination of surface and bulk micromachining technologies, and has been widely applied in mechanical filters, accelerometers, gyroscopes, optic modulators, and radio frequency (RF) passive devices. Generally, a MEMS comprises circuits and microstructures. U.S. Pat. No. 5,717,631 proposed a MEMS structure and process of making the same, which had the disadvantage of the generation of an undercut on a substrate under circuits or other structures adjacent to the microstructure during the release of the microstructure, thus the processing parameters must be precisely controlled in order to prevent over-etching from occurring, and protect the substrate under circuits or other structures adjacent to the microstructure from being damaged due to excessive undercut. In addition, noises generated from different circuits would be transmitted via the substrate and lead to interference between the circuits. Conventionally, such interference is prevented by using guard rings, or by allocating circuits that are prone to generating noises away from other circuits. However, the guard rings block noises by forming wells on the substrate, and its effect of blocking off noises is limited, while allocating circuits that are prone to generating noises away from other circuits requires the use of chips with larger surface area, which increases further costs for manufacturing and impedes the aim of miniaturization.
Therefore, it is desired a MEMS and process of making the same that do not increase manufacturing costs, may lower interference between circuits thereof, and may prevent over-etching.